1. Field of Invention
The invention relates to an overvoltage protection device for protection of low voltage electrical installations, having a device base part with terminals for phase conductors (L1, L2, L3) and ground or neutral conductors (PE, N) and of at least one overvoltage protection element, with an arrester which is located in a housing, especially a lightning and/or surge arrester, the base part of the device having at least one telecommunications contact which has a switch for remote indication of the state of at least one overvoltage protection element, and preferably, the base part of the device having plug-in contacts which are connected to the terminals and which are made especially as sockets, and the overvoltage protection element having corresponding connector contacts made especially as plug pins so that the overvoltage protection element can be plugged onto the base part of the device.
2. Description of Related Art
Electrical, but especially electronic measurement, control and switching circuits, mainly also telecommunications equipment and systems, are sensitive to transient overvoltages, as can occur especially by atmospheric discharges, but also by switching operations or short circuits in power supply grids. This sensitivity has increased to the extent electronic components, especially transistors and thyristors, are being used; in particular, increasingly used integrated circuits are highly endangered by transient overvoltages.
Electrical circuits normally work without problems using the voltage specified for them, the rated voltage (generally the grid voltage). This does not apply when overvoltages occur. Overvoltages are considered to be all voltages which are above the upper tolerance limit of the rated voltage. They also include mainly transient overvoltages which can occur due to atmospheric discharges, but also due to switching operations or short circuits in power supply grids, and can be galvanically, inductively or capacitively coupled into electronic circuits. In order to protect electrical or electronic circuits, especially electronic measurement, control and switching circuits, mainly also telecommunications equipment and systems, wherever they are used, against transient overvoltages, overvoltage protection elements have been developed and have been known for more than 20 years.
The required measures for protection of the power supply of installations and devices are divided into different stages, depending on the choice of arrester and the expected ambient influences. The overvoltage protection devices for the individual stages are distinguished essentially by the level of arresting capacity and the level of protection.
The first protection stage (type 1) is generally formed by a lightning arrester which is installed as an extremely high power protection device in the central power supply of a building. An important component of such a lightning arrester is a spark gap with at least two electrodes, an arc being forming between the two electrodes when the spark gap is ignited.
The second protection stage (type 2) generally forms a varistor-based surge arrester. This protection stage again limits the remaining residual voltage over the lightning arrester. Depending on the hazard potential of the installation which is to be protected or the building which is to be protected, it can be sufficient in the individual case if the second protection stage, i.e., the surge arrester, is used to start.
In addition, there are triggered-type lightning arresters which are based on the AEC principle (active energy control) and which constitute a combination of a lightning arrester and surge arrester. In this arrester combination, lightning and surge arresters can be connected directly in parallel. This is especially advantageous when the lightning and surge arresters cannot be installed spacially separate from one another.
Within the framework of this invention, the above described versions can be called arresters without the intention to limit the invention to one special arrester type. Such an arrester then forms the significant component of an overvoltage protection element, the overvoltage protection element having at least one housing which holds the arrester.
Known overvoltage protection devices for connection to electrical lines have a device base part which can be mounted, for example, on a supporting rail. For installation of such an overvoltage protection device which is designed to protect, for example, the phase-carrying conductors L1, L2, L3 and the neutral conductor N, and optionally also the ground conductor PE, in the known overvoltage protection devices, on the base part of the device, there are corresponding terminals for the phase conductors and the ground and neutral conductor. In the overvoltage protection device underlying the invention (Phoenix Contact brochure “Overvoltage protection TRABTECH 2002, pages 24 & 25), the base part of the device has an asymmetrical connection pattern. In the known overvoltage protection device in which the base part of the device is made roughly U-shaped, on one leg there are the terminals for the phase conductors and the neutral conductor and on the other terminal leg there is the terminal for the ground conductor.
For simple mechanical and electrical contact-making of the base part of the device with the respective overvoltage protection element, in the known overvoltage protection device, the overvoltage protection elements are made as “protective plugs”, i.e., the base part of the device has sockets connected to the terminals and the overvoltage protection element has the corresponding plug pins, so that the overvoltage protection element can be plugged onto the base part of the device. In addition, the known overvoltage protection device has another changeover contact as a sensing element for remote indication of the state of at least one overvoltage protection element, for this purpose, in the base part of the device, there being a switch, and on the overvoltage protection element, there being an actuating element.
In the known overvoltage protection device, installation and mounting are very simple and time-saving due to the plug-in capacity of the overvoltage protection elements. The telecommunications contact enables easy remote monitoring. However, moreover, it can also be desirable to be able to read the state or status of the overvoltage protection element directly on site. But it is a problem here that, especially in overvoltage protection elements which are made as “protective plugs,” only relatively little space is available in the housing.